Air Pressure

6.3.2.3 Air Pressure / Study Guide

Just like all matter, air has mass. Earth's gravity holds the atmosphere in place. This also causes air to exert a pushing force on the things around it called air pressure.

Air pressure decreases the higher you get into Earth's atmosphere, and is strongest near Earth's surface.

Multiple Choice

_________ holds Earth atmosphere in place.

• Magnetism

• Gravity

• The jet stream

• Rope

Multiple Choice

Where would you expect to feel the most air pressure?

• on a space shuttle in its orbit around Earth

• outside of Earth's atmosphere

• the bottom of a valley

• the top of a mountain

Multiple Choice

Where would you find air particles spaced farthest apart?

• Point A

• Point B

• Point C

• Point D

• Point E

Air Pressure Changes

The temperature of air can also change the air pressure. Warm air rises and creates less pressure. Warm air is lighter than cool air because the particles in warm air are farther apart. When particles are farther apart, the air has less mass to press down on an area. When air is cooler, the particles are closer together. This creates more weight and causes the air to sink. Because cooler air has more mass, it creates more pressure.

Another way to think of this concept is to pretend air particles are like marbles. If you had more marbles in a jar, the jar would be heavier than a jar with fewer marbles. Air works in a similar way.

The Sun heats areas of Earth differently. This causes some areas to be warmers than others and creates areas of warm and cool air with different levels of air pressure.

Multiple Choice

Choose the arrow that best shows how warm air affects air pressure.

Multiple Choice

Choose the arrow that best shows how cool air affects air pressure.

Multiple Choice

All areas of Earth are heated evenly by the Sun.

Multiple Choice

Bill and Mary are from two different areas of the United States. Based on the diagram, ________ is probably in an area with higher pressure

Multiple Choice

Bill and Mary are from two different areas of the United States. Based on the diagram, ________ is probably in an area with lower pressure

Air pressure can be used to help us predict the weather. A barometer is a tool used to measure air pressure.

The mercury barometer on the right is made by sealing mercury (a silver, liquid substance) inside a tube and setting the tube in another pool of mercury enclosed in a pan. The air pressure presses on the pan to push the mercury up the tube to different heights depending on how high or low the pressure is outside.

Air pressure can be used to help us predict the weather. A barometer is a tool used to measure air pressure.

The barometer on the right is called an aneroid barometer. It has a small, flexible metal box that will expand when th

Multiple Choice

If the air pressure decreases, the needle of the barometer will

• Move right

• Move left

• Not move

Multiple Choice

Who probably uses a barometer the most?

Multiple Choice

Barometers work because air pressure exerts _______.

• a pushing force

• magnetism

• a pulling force

• gravity

• magic

Air Pressure and Weather

Air pressure has a big effect on the weather. Low pressure means that warm air is rising. As warm rises, it cools. Water vapor in the cooler air condenses, which forms clouds that can cause rain, snow, and storms.

High pressure means that cool air is sinking. As cool air sinks, it takes the water vapor with it. Clouds and storms cannot form as easily in areas of high pressure, so an area of high pressure usually has sunnier or nicer weather than an area of low pressure.

When a barometer's reading is higher, it means the air is currently experiencing high pressure and that sunny, clear, or mild weather is more likely.

When a barometer's reading is lower, it means the area is currently experiencing low air pressure and that rainy, stormy, or poor weather is more likely.

Multiple Choice

Based on the barometer to the left, the area where it is located is most likely _____ air pressure.

• low

• high

Multiple Choice

Air pressure is _______.

• a mixture of gases that surrounds a planet

• the condition of the atmosphere at a given time and place

• the rising and sinking of gases, liquids, or solids in a circular path

• a pushing force that air exerts on an area

Multiple Choice

What is a barometer?

• a tool that measures air pressure

• a mixture of gases that surrounds a planet

• the rising and sinking of gases, liquids, or solids in a circular path

• the condition of the atmosphere at a given time and place

Multiple Choice

More air pressure

• Troposphere

• Exosphere

Multiple Choice

Air particles closer together

• Troposphere

• Exosphere

Multiple Choice

Air particles farther apart

• Troposphere

• Exosphere

Multiple Choice

Less air pressure

• Troposphere

• Exosphere

Multiple Choice

Choose the type of air pressure that this location is mostly likely experiencing.

• lower air pressure

• higher air pressure

Multiple Choice

Choose the type of air pressure that this location is mostly likely experiencing.

• lower air pressure

• higher air pressure

Multiple Choice

Which object would be used to measure air pressure?

Multiple Choice

Air pressure exists because air has mass that pushes down on Earth because it is being pulled by ______.

• gravity

• magnetism

• barometers

• jet streams

Multiple Choice

Areas of low and high pressure exist on Earth because _______.

• gravity pulls on air differently depending on the time

• air particles escape from Earth's gravity at night

• the Earth's oceans keep the Earth heated evenly

• the Sun heats areas of the Earth unevenly